Metal-metal bonding and interstitials in reduced rare earth metal halides

Abstract

Exploratory research in recent years has shown that the rare earth elements in their highly-reduced halides exhibit a remarkable ability to undergo cluster formation, some as isolated units, and others as infinite chains or slabs containing double-metal layers. Only a few of the elements have been studied in any detail, principally scandium, yttrium and gadolinium. Many of these new compounds are uniquely stabilized by a second-period element bound within each cluster, e.g. in Sc 7Cl 12B, Sc 5Cl 8C, Y 2C1 2C and Li y YClH x , although a few structures evidently represent true binaries, e.g. Sc 7Cl 10 and Y 2C1 3. The known phases and their structures are briefly reviewed and some relevant information from extended-Hückel band calculations and UV photoelectron spectroscopy are noted.